In data processing systems, especially in a complex baseband chip of a wireless transceiver, frequently a ROM is used to store code and data, in particular to store the firmware of the system or parts thereof. In case of a baseband chip the ROM is frequently integrated on the baseband chip. Often there is a need to update the information in the ROM. Reasons for updating are the need to fix bugs in code and/or data in the ROM or the need to include new or custom functions. Since the information in the ROM is mask-programmed, the information is fixed and cannot be directly updated without modifying the fabrication masks of the ROM or the complete baseband chip in case of an integrated ROM. Additionally, an update of an already fabricated ROM by directly rewriting the fabricated ROM is not possible.
Conventionally, the information on the ROM is updated by patching those blocks of the ROM which need to be updated. According to conventional ROM patching techniques patches, updated blocks of information and the corresponding patch addresses, are loaded in a patch hardware, containing a patch RAM (random access memory) for storing the updated blocks and a set of address registers for storing the patch addresses. In case one of those patch addresses in the ROM is addressed during operation, the patched block in the patch RAM is read instead of the original block in the ROM. Thus, the patch hardware works as cache. The patching capability of this conventional cache-like technique is limited according to the maximum number of patches to load.